Compensated winding



Jan. 1,`1957 COMFENSATED WINDING Filed Nov. 4, 1952 mmm WWW/W; g

Aria/wrs 2,776,417 Patented `lan. 1, 1957 CMPENSATED n il,-

Application November 4, 1952, Serial No. 318,720

18 Claims. (Cl. 340-11) My invention relates to an improved core and winding construction for electro-magnetic circuit elements and is of application to electro-acoustic transducers, to electro-magnetic inductors, to transformers, and the like.

It is an object of the invention to provide improved devices of the character indicated.

lt is a specific object to provide an improved core and winding construction having the basic virtues of toroidally wound cores without requiring the elaborate fabrication techniques necessary with toroidal windings.

It is another specific object to provide an improved construction of the character indicated in which stray hum and other pickup may be completely and inherently compensated for and, therefore, eiectively neutralized.

Other objects and various further features of novelty and invention will be pointed out, or will occur to those skilled in the art from a reading of the following specification in conjunction with the accompanying drawings. In said drawings, which show, for illustrative purposes only, preferred forms of the invention:

Fig. l is a longitudinal sectional View through an electro-acoustic transducer incorporating features of the invention;

Fig. 2 is a sectional View in the plane 2-2 of Fig. l;

Figs. 3 and 4 are simplied fragmentary views partially in section and illustrating alternate employments of my transducer in electro-acoustic arrays; and

Figs. 5 to 8 are simplified longitudinal sectional views of alternate circuit elements incorporating features of the invention.

Briefly stated, my invention contemplates a new core and winding construction employing what may be termed a toroidal core with a iirst, or signal winding, coupled to the core path and to the stray-ilux path, and with a second, or compensating winding, coupled to the stray-ilux path to the exclusion of the core path. The iirst and second windings may have substantially the same number of turns and may be connected in opposition, so that any coupling to the stray-flux path will be completely neu tralized, and coupling to the core, will, in eect, be exclusively promoted. In application to electro-acoustic transducers, the core may be of magnetostrictive material, at least in those parts of the core in which magnetostrictive elongations are desired. Thus, in one general form of the invention, the toroidal core may comprise two generally concentric elongated tubular magnetostrictive members with magnetic means radially closing and interconnecting the ends of said cylinders to detine the toroidal ux path. ln application to circuit elements, the same general core construction may be employed, or the tubular members may be integrally formed with endilange means to complete the toroidal path when tubular members are assembled to each other. By way of illustrating circuit-element applications, I shall also describe a transformer construction and an inductor construction.

Referring to Figs. l and 2 of the drawings, my invention is shown in application to an electro-acoustic transducer specifically designed for underwater use. As indicated generally above, the construction features a toroidal core which happens in the form shown to be built up from a plurality of elements designed to promote principal acoustic response generally along the axis of the toroid. The core elements may thus comprise inner and outer tubular members lil-11 of magnetostrictive material, as, for example sheet-metal alloy comprising substantially 49 percent iron, 49 percent cobalt and 2 percent Vanadium. The sheets may be relatively thin and overlapped at their longitudinally extending edges, as at 12-l3, after applying a thin layer of insulation between the overlapping areas in order to reduce circulating eddy currents. The toroidal path may be completed by means of end closure caps 14-15 of magnetic material in magnetic-flux-conducting relation with both cylinders 10-11. For simplicity of fabrication, I have shown the end members lill5 to be circular discs cf magnetic ceramic material, such as a ferrite.

In accordance with a feature of the invention, two windings are employed in particular relation with the core means described. Such windings may include a rst or signal winding 16 linked to the core and also to the strayliux path passing through the center of the toroid, i. e. within the inner cylinder 10; the second or compensating Winding 17 is wholly linked to the stray-flux path to the exclusion of the core path and may, therefore, be contained within the inner tubular member 10. In order to achieve full compensation for stray ilux, the number of turns on the two windings 16-17 is preferably the same, and these windings are connected in opposition, as suggested by the portion i8 of the conductor material interconnecting the right end of the two windings through a small opening in the tubular member 10.

rthe entire transducer may be contained within a housing 19, which may be a metal casting, and pressure-release means 2t), such as a layer c'f cork or air-lled rubber, may line the excavated interior of the housing 19 and, therefore, peripherally envelop the toroidal core. Diaphragm means 2l may flexibly seal off the housingv opening, and leads to the two windings may be carried out the closed end of the housing, as to a lead cable 22 passing through a suitable end tting 23.

lt will be seen that the described construction lends itself to relatively simple fabrication with common coilwinding machines and techniques; for example, the inner winding 17 may be applied as a continuous helix on a cylindrical form, such as a cardboard roll or a plastic rod or tube, as shown at 24. ln a separate and equally simple operation, the outer winding 16 may be applied as a single continuous helix over the periphery of the inner tubular member 10; of course, to preserve insulation, the wire itself may be insulated as, for example, enamelcoated, or the cylinder it) may be coated with insulating material before applying the winding 16.

Having made the two simple conventional windings 16-17, they may be interconnected at 1S in a simple soldering operation, and the leads brought out through small openings 25-26 in the rear-end plate 15 of the core. The plate 14 may then be applied, and the entire wound core assembly immersed in a potting compound so as to fill air spacesat 27-2Sg the potting compound at 27-28 is preferably of the sound-transmitting characteristics of the medium (e, g. water) in which the transducer is to be employed, and with vacuum-immersion the potting material may be brought into intimate pressuretransmitting relation with all exposed active internal surfaces of the transducer (i. e. surfaces of cylinders l--ll and of end plates 14--15). The basic transducer unit may then be inserted in the housing 19, which may previously have been lined with the pressure-release material 20, and the assembly may be made completely rugged 4 by further potting in the space 29. Finally, in order to seal off all possible crevces, a. boot or coating 3) of plastic, rubber, or rubber-like material may be applied over the entire assembly, as in a dipping process.

`In Figs. 3 and 4, I show alternate employments of my basic transducer construction, as in multiple-element arrays. In Fig. 3, the array comprises within a housing 35 a plurality of independent core units or transducer elements 36-37-38-39, each of which may be of essentially the same construction as that part of the structure of Figs. l and 2 as is fully contained within the toroidal core --11-14-15 It will be understood that lead connections and winding interconnections have been omitted in Fig. 3 for the sake of clarity, but that for eac-h transducer element the leads may be brought out of the rear end in the manner described in Fig. 1, and interconnected to each other by known methods to achieve directional or other array functions. The array is cornpleted in Fig. 3 by having all active faces 14 of the cores of transducer elements 36-37-3S-39 aligned in essentially the same thrusting surface and intimately related to a common diaphragm 4), which may be peripherally bolted, as suggested at 41, to the housing 35. Lateral pressure-release means such as cork liners may effectively envelop the transducer units of Fig. 3, but for certain applications the desired lateral release may be achieved by merely not lling the spaces between these elements and, therefore, by leaving them exposed to air within the remaining volume in the housing 35.

In Fig. 4, the array is contained within a housing 45 which may be the same as that described in Fig. 3 and, again, common diaphragm means are applied over all transducer elements. However, in Fig. 4 the transducer elements are never completed until fully assembled into the array. This is because end closures for the toroidal cores are formed at one end by a single plate 46 of magnetic material, as of magnetostrictive ceramic, and at the other end by a similar plate 47.

In assembling the array of Fig. 4, therefore, the inner and outer cylinders PrO- 1l may be assembled and wound and potted in the manner already described, except that end-closure plates are omitted in this preliminary assembly. Toroidal cores are completed only when the end plates 46-47 are applied in place. The end plates 46-47 may be retained by tie-bolts (not shown) extending therebetween, but suicient adhesion of the assembly may result if the wound core elements 10-11 are potted with a slight excess of potting material, so that upon localized heating of the plates 46-4'7, when squeezed to the wound tubular members lil-11, the plastic itself will be permitted to permeate the microscopic interstices of the plates 46-47, so as to provide a suiciently rigid bond upon setting of the plastic. Thus, in Fig. 4 the basic array is seen to be completed again by employment of common diaphragm means, and the diaphragm means in Fig. 4 may he viewed as constituting either the forward thrust plate 47, or the combination of the plate 47 with the flexible diaphragm 43.

In Fig. 5, I show an application of the principles of my invention to a circuit element which may be a transformer. The circuit element is seen to comprise a toroidal core including inner and outer tubular members Sti-51, between end-closure pieces 52-53. A first signal winding 54 is linked to the `core and to the stray-linx path, and a first compensating winding 55 is linked only to the strayux path and is connected in opposition to the signal winding 54. The described windings 54- 55 represent a cornplete parallel with the construction of Fig. l and may constitute the primary of the transformer. The transformer secondary may include a signal winding 56 linked to thesame core and .also to the stray-'flux path, and a compensating winding 57 linked only to the stray-duri path. The secondary windings 56-57 may also be connected in opposition, and primary and secondary 'leads may be `brought out through appropriate access holes at opposite ends of the device, as -at 58-.59,'respectively.

4 For Complete compensation and assurance against .stray pickup, I prefer that the signal and compensating windings 54-55 for the primary shall have the same number of turns, and that the secondary (signal and compensating) windings 56-57 shall also have the same number of turns, as will be understood.

In Fig. 6, I illustrate a slight variation of the basic construction wherein the toroidal core is made entirely of magnetic ceramic material. Thus, inner and outer tubular members 60--61 may be ceramic cylinders, and the toroidal paths may be completed by ceramic end plates 62-63- The signal and compensating windings 64-65 may be coupled to the core and to the stray-flux paths, as described above. The device of Fig. 6 will be seen to represent a good electroacoustic transducer contiguration, or merely a circuit-element inductance; and, of course, the inherent freedom of magnetic ceramics from eddy-current problems avoids the necessity of resorting to insulated overlapping ends (as at 12-13 in the construction of Figs. l and 2). Thus, the cylinders 60-61 may be circumferentially continuous.

In Fig. 7, I illustrate a simplified transducer or circuitelement construction, 'wherein the toroidal core is made up of two parts which may be said to include inner and outer tubular members 67-63 with cooperating end flanges 69-'70 to complete the toroid. Thus, the inner tubular member 67 may be integrally formed at one end with a radial outwardly extending iiange 69, and the outer tubular member 68 may be integrally formed at the other end with a radial inwardly extending flange 76. It will be noted that the ange 7) extends all the way radially inwardly so as to make the part 68-76 constitute a cup with a closed bottom. Assembly may be made by applying the signal winding '7l to the outer surface of the inner tubular member 67 and by bringing one lead thereto through a small access opening 72 at the base of ilange 69. The inner, or compensating winding 74, may be applied to a projection 75 integral with a plastic closure 7 6 for one end of the device. Leads 73-77 may both be brought out through the base of the plastic closure 76; and, if desired, a further plastic layer 78 may be applied, as by dipping, to encase the entire device or to complete its enclosure, as suggested at 7 8.

In Fig. 8, I illustrate another transformer embodiment, which may generally resemble the construction of Fig. 5. Thus, in Fig. 8, a toroidal magnetic core may be established by cylinders 863-81, capped by end plates SZ-SS. A signal winding 34 may be linked to the core and to the stray flux, and a compensating winding may be linked to the stray flux to the exclusion of the core. The electrical input and output connections 86-87, respectively, illustrate an autotransformer use of the described parts. Thus, input leads 86 may be connected across a small number of the turns of signal winding 34, and output leads 87 may be connected across the full signal winding 84. The compensating winding 85 need not be connected as an autotransformer, and I have illustrated connection of winding 85 merely in series with one output pole of the signal winding 84. With the compensating winding 85 thus connected in opposition to the signal winding output, full neutralization of stray-flux pickup may be achieved without the need to connect the compensating winding as an autotransformer.

It will be seen that I have described a basically simple winding `and core construction lending itself to massproduction techniques which are already well understood and for which there is a relative abundance of machinery. My construction avoids the undesirable properties (i. e. susceptibility to stray tlux) characteristic of helicallywound constructions made with such existing techniques and machinery. While it has been possible in the past to avoid these undesirable characteristics by resorting to complex fabrication methods and expensive machinery,

my construction avoids the need for such complexity and expense.

While I have described the invention in detail for the preferred forms shown, it will be understood that modifications maybe made within the scope of the invention as deiined in the claims which follow.

I claim:

1. In a device of the character indicated, a hollow core of magnetic material defining an annular space within said core, saidvcore having a central opening on the axis thereof, a first winding within said annular space and developed generally along said axis, whereby a generally toroidal flux path may be established in said core, and a second-,winding within said opening and developed generally along said axis, whereby upondifferential connection of said windings stray-field edects common to both windings may be substantially eliminated.

2. In a device of the character indicated, magnetic-core means establishing a continuous generally toroidal path, .said core means having a central opening on the axis thereof, a rst winding linked to said path and developed generally along said axis, whereby said iirst winding is also linked to the stray-flux path through the axis of said core means, and a second winding within said opening and developed generally along said axis and therefore linked only to said stray-linx path, said windings being,

dilerentially connected, whereby stray-field effects common -to both windings may be substantially eliminated.

3. A device according to claim 2, in which the number of turns of each of said windings is substantially the same.

4. A device according to claim 2, in which said core means includes a magnetic ceramic.

5. A device according to claim 2, in which axially extending parts of said core are of magnetostrictive material.

6. In a device of the character indicated, two substantially concentric elongated cylinders of magnetic material, a rst winding enveloping the inner of said cylinders andwithinthe outer of said cylinders, a second winding developed generally on the axis of saidkrst winding and wholly Within the inner of said cylinders, and closure means of magnetic material radially interconnectingrthe ends of said inner and outer cylinders, whereby a toroidal ux path is defined withV said iirst winding linked to said tlux path and with said second winding independent of said path.

7. In a device of the character indicated, two elongated magnetostrictive tubular members one within the other and magnetically interconnected at their corresponding ends, whereby a generally toroidal ux path is thereby dened, a first winding in the radial space between said members and therefore coupled to said ux path, and a second winding radially within the inner of said members, and therefore not coupled to said ux path, whereby upon dilferential connection of said windings strayfield effects common to both windings may be substantially eliminated.

8. A device according to claim7, in which said tubular members are axially substantially coextensive, and in which the interconnection of said members is effected by end closure members of magnetic material in intimate magnetic-flux-eirculating contact circumferentially continuously of both said tubular members.

9. Adevice according to claim 7, in which the interconnection of said members is effected by radial-flange means carried by one of said tubular members.

12. In a multiple-element transducer of the character indicated, a plurality of cores of magneto-strictive material establishing for each core a generally toroidal ux path, said cores being aligned with their thrust faces substantially in a common surface, there being for each core a first winding linked to the core path and to a stray-flux path, and a second winding ditferentially connected to said first winding and located radially inside said toroidal ux path and linked solely to the stray-flux path, and diaphragm means common to the thrust faces of all said elements.

13. A transducer according to claim 12, in which said cores are completely self-contained separate and independent elements, and in which said diaphragm means is separately connected to each of said units.

14. A transducer according to claim 12, in which the thrust end of each of said cores is closed by a single piece of magnetic material common -to all thrust ends of said cores and separately closing the toroidal ux paths in all of said units, whereby said single common piece of magnetic material constitutes said diaphragm means.

15. An electro-acoustic transducer, comprising a magnetic core including magneto-strictive means at least in axially extending parts thereof and establishing a generally toroidal ux path, said core having a central axially extending opening therein, a rst winding coupled to said core and developed generally along the axis of said core, a second winding differentially connected to said rst winding and developed generally along said axis within said opening, and pressure-release means circumferentially enveloping the periphery of said core.

16. In a transducer of the character indicated, a relatively rigid housing having an excavated interior opening to one end thereof, aV magnetic core establishing a generally toroidal ilux path and including magnetostrictive means in the parts of said core which extend axially out of said opening, said core having a central axially extending opening therein, a rst winding linked to said core and developed generally along the axis of saidV core, a second winding differentially connected to said first winding and developed generally along said axis Within said central opening, pressure-release means radially isolating said core from said housing, and a diaphragm in intimate axially directed pressure-transmitting relation with that end of said core which faces out of said housing opening.

17. A transducer according to claim 14, in which a second similar piece of magnetic material closes the other ends of all said core units in common.

18. In a device of the character indicated, a core comprising two elongated cylindrical members of magnetic material one within the other and magnetically interconnected at their corresponding ends, a first winding inthe radial space between said members and therefore coupled to said core, and a second winding substantially axially coextensive with said rst winding and radially Within but independent of effective coupling to said core, whereby upon differential connection of said windings stray-held effects common to both windings may be substantially eliminated.

References Cited in the le of this patent UNITED STATES PATENTS 433,702 Tesla Aug. 5, 1890 1,287,982 Hartley Dec. 17, 1918 1,289,418 Elmen Dec. 31, 1918 1,966,446 Hayes July 17, 1934 2,076,330 Wood Apr. 6, 1937 2,153,571 Kallmeyer Apr. 11, 1939 2,249,835 Lakatos July 22, 1941 2,496,484 Massa Feb. 7, 1950 2,638,577 Harris May 12, 1953 

